Composite materials, articles of manufacture produced therefrom, and methods for their manufacture

ABSTRACT

The invention is directed to a plastic fiber article of manufacture having composite-like high strength characteristics. The article of manufacture can be in the form of a panel or board. The panel or board is constructed from low cost fiber materials, industrial grade or high thermal plastic, and other additives to protect the board or panel from ultraviolet light, fugii growth, excessive heat, fire, insect infestation, and/or weathering. The plastic fiber panel or board may be textured and colored to resemble natural wood such as cedar, walnut, or oak. The plastic fiber panel or board is stronger more durable and may be cheaper than natural wood alternative panels or boards.

FIELD OF INVENTION

The present invention relates to a composite material, articles ofmanufacture produced from the composite material and a method ofproducing articles of manufacture from the composite material.

BACKGROUND OF THE INVENTION

Wood has been milled into various different shapes for use as structuralor decorative components in the building industry, as components infurniture, railcars, trailers, and the like for many, many years. Wood,while structurally strong, useful and well adapted for use in manyresidential and commercial situations, can have problems under certaincircumstances related to the deterioration of the wood components.Another potential problem with using wood for structural components isthat the stronger woods are considerably denser than weaker woods, andas a result, tend to be very heavy. This is specifically problematicwhen weight is a concern. To overcome this problem a straight compositesuch as fiberglass or carbon fibers can be used which is stronger andlighter than hard woods. It is true that the straight composites providesuperior strength with light weight, but the cost is extraordinarymaking these materials useful only in high value situations. Generally,these composites cannot be used cost effectively in normal woodreplacement type applications.

Thus, when an application requires that the wood component be verystrong, i.e., a weight bearing wall, hard wood, pretreated soft wood orreinforced soft wood is preferred and as a result the weight of thestructure is excessive. Therefore, there is a need for a material thatcan provide strength without adding excessive weight, and extraordinarycost to the structure where these materials are used. In addition, dueto the increase in cost of the milling processes, the reduction insupply, and the increase in the cost of treating lumber, wood productsare slowly becoming more expensive as demand increases. Although woodsubstitutes are currently available (made as a first generation productusing recycled polyethylene), it is believed that no one wood substituteprovides the strength of real wood, with a decrease in the weight andcost of the final product. In fact, wood is 2-5 times stronger thancurrent wood replacement composites. Wood replacement composites arealso very expensive and may cost 2-3 times the cost of constructiongrade lumber or 20-30% more than treated high grade soft woods.

Accordingly, a substantial need exists for an improved compositematerial that is equally strong or stronger than traditional milledwoods, weights less than milled wood, is maintenance free and is lessexpensive than milled wood. The present invention provides a compositematerial that can be shaped to produce articles of manufacture thatpossesses the favorable aspects of wood without the negative aspectsdescribed above.

SUMMARY OF THE INVENTION

The invention is directed to an article of manufacture comprising afiber material and a thermal plastic. The fiber material may be wood,fiberglass, agricultural by-products, industrial by-products or anyother material having a durable wood- or fiber-like consistency. Thefiber materials can also be a mixture of different fibers, such as woodand fiberglass, wood and agricultural by-products, etc. The article ofmanufacture may contain between about 40% to about 70% by weight of thefiber material and about 0.1-30% by weight of the total weight of thearticle of manufacture of additives. The remainder of the compositematerial used to make the article of manufacture consist of the thermalplastic material.

The thermal plastic material of the article of manufacture may bepolyethylene or polypropylene. This material aids in binding the fibermaterial together so as to form a strong, durable article ofmanufacture. In fact, the thermal plastic material actually shrinks togrip the fiber material so as to hold the fiber material in place, asthe thermal plastic cools. The article of manufacture may containbetween about 30% to about 60% by weight of thermal plastic.

The invention is also directed to a process of producing the article ofmanufacture. This process produces an article of manufacture comprisingfiber material, thermal plastics and additives. The process may use anyone or combination of the fibers discussed above. For example, when woodis used in making the article of manufacture, the fibers are firstscreened through a 20-40 mesh screen and added to a mixing container.The screened fibers are than heated to remove moisture so that airpockets do not form when the water is converted into steam as the fibermaterial is processed.

Hot thermal plastic material is then added to the mixing container sothat it comes in contact with the screened fibers. The thermal plasticmaterial may be added to the screened fibers by injecting the thermalplastic material into the mixing containers. Injection of the hotthermal plastic material into the mixing container allows for precisemeasuring of the amount of thermal plastic material added to themixture. Additives are added to the plastics stream as it is heated,melted and mixed.

Once the screened fibers are mixed with the hot thermal plastic, theresulting mixture is then placed in contact with a die. The die is usedto produce the shape of the article of manufacture. Once shaped, thearticle of manufacture is cooled and cut to a desired shape and length.For example, the article of manufacture is cut with an inline saw.Alternatively, the article of manufacture can be directly extruded tothe desired shape.

When fiberglass is used as the fiber material instead of wood, thefiberglass is chopped into ¼, ½ or ¾ inch lengths. Once the fiberglassis the correct size, the fiberglass chop is substituted for wood in theprocess described above on a weight basis. When fiberglass is mixed withwood to make the composite, fiberglass chop is added to the screenedwood and the process described above is unchanged.

In another embodiment, fiberglass can be added to the process as aTwintex™ pellet having 60% fiberglass co-mingled with 40% polypropylene.The percentages may vary and are referred to as the load. The Twintex™pellets can be chopped in the same ¼,½ or ¾ inch lengths as discussedabove. Because this is a polypropylene co-mingle the pellet isintroduced into the thermal plastic barrel rather than the wood barrelof the extruder.

The article of manufacture produced is durable, strong, and longlasting. These characteristics make the article of manufacture a goodreplacement for wood, and other structural and decorative materials inplaces where conditions are extreme and other materials have a shortlife span. For example, the article of manufacture can be used in theconstruction of decks, floors, sidewalls in railcars, trucks andtrailers as well as fences and residential home construction.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 shows a schematic diagram of a panel having a pattern of “voids”which is made from the composite invention.

FIG. 2 shows a schematic diagram of a panel having a pattern of “voids”different from that of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to an article of manufacturecomprising a composite material as well as a process for making thearticle of manufacture. The preferred composite material has acontrolled water content which ensures high quality physical propertiesin the articles of manufacture that are produced from the compositematerial.

The composite material may contain fibers from a variety of differentsources such as wood, fiberglass, industrial by-products andagricultural by-products. Wood fibers that can be used to make thecomposite material include, but are not limited to, fibers from oak,birch, cedar, maple, and other types of hard wood trees. Fiberglass thatcan be used to make the composite can be in the form of “chop” or in apelletized form that is commercially available. Fiberglass may also beused that is already mixed (co-mingled) with polypropylene into strandsor pellets. This mixture is also commercially available. Fiberglass canbe added to or can be used to replace wood fiber on a one to one basis,however, the increase in cost of fiberglass can be prohibitive. All inall, the choice to use wood, fiberglass, or a fiberglass and woodmixture, can be decided on an individual customer basis.

Industrial by-product fibers that can be used to make the compositeinclude mica industrial by-products. These are sometimes used to addstrength, fire retardation or moisture resistance. Agriculturalby-product fibers that can be used to make the composite includecornstalks, wheat straw, sisal, bamboo reeds, and hemp as well asothers.

Cost, availability and stable supply make wood fibers (880 Million tonsa year go to land fills) the preferred fiber source for the compositematerial. Special needs such as using fiberglass as a fiber source toincrease strength of the composite, however, might justify the use ofany one of the other fibers listed above, regardless of the increasedcost of the fibers as compared to wood.

The composite material contains about 40% to about 70% of fiber materialby weight. Preferable, the composite material-contains about 60% offiber by weight. More preferably, the composite material contains about50% of fiber material by weight.

The amount and type of fiber material used to make the compositematerial will effect the strength, weight and density of the article ofmanufacture produced from the composite material. If the fiber materialused is very dense, the quantity of this fiber used to make thecomposite may be lower than if a less dense fiber material is used.While weight may be less than other materials, the real trade off withusing a composite material compared to a cheaper alternative is that fora slight increase in cost the product is maintenance free.

One composite embodiment of the invention, uses, a wood chip plastic mixand does not have the same characteristics of a normal high cost, highstrength composite such as pure fiberglass. Because the wood chipplastic mix takes on the characteristics of the wood chip itself, itacts very similar to wood. In other words, it is very dense (we replacethe cellular air spaces with plastic which makes it as much as 20 to 30%heavier then wood) and in most cases heavier than wood. To eliminateweight, some producers use foaming agents to put air pockets or cells inthe composite giving it a wood like characteristic. In the presentinvention, a computer is used to optimize a profile that maintains thestrength (because of the design) but lowers the weight. Even in thesecases, the composite material is only slightly lighter than the wood itreplaces.

The designs shown in FIGS. 1 and 2 are proprietary designs that aid inproviding the same or greater strength of a full panel made of wood(depending on the fiber source and additives used), while being the sameor slightly less in weight. All in all, the main advantage of thecomposite is not that it weighs less than wood, but rather that it ismaintenance free, i.e., the bugs will not eat it. It will not rot, splitor crack and never needs to be painted.

An article of manufacture made from the present invention is made withpolypropylene and is formed in the design shown in FIGS. 1 and 2 and hasthe strength of wood. The strength of this product is achieved using anengineered polymer (i.e. BP Amoco 9433 polypropylene). Using theengineered polymer increases or maintains the strength of wood but keepsthe cost at about the same level as wood. In other words, the cost ofthis product is very similar to first generation type products, but,wood is still a cheap alternative. As stated above, the trade offbetween wood and composite is that the composite is maintenance free andhas a considerably longer half life as compared to wood.

Alternatively, fiberglass chop or pellets can be used to replace wood ona one to one weight basis. This provides increased strength to thecomposite but may increase the cost of the final product. In situationswhere increased strength is required, fiberglass can be used to replacewood fiber. For example, a mix of 60% ½ inch fiberglass chop and 40%polypropylene would have a flex modulus (modulus of elasticity) of 2.5Million or higher (compared to oak at approximately 1.8 Million).Similarly, a mix of 35% fiberglass chop, 25% wood fiber, and 40% plasticwould have a flex modulus (modulus of elasticity) of about 1.6-1.7Million which is equivalent to oak. In addition, this product would alsohave a tensile modulus of about 25,000 which gives it twice the strengthof high end oak. Straight fiberglass chop may also be used to make thecomposite.

If straight fiberglass chop is used, it can be added to the wood streamas a straight fiber source. In other words, the fiberglass can be feddirectly into the extruder, at the same time as wood. As the wood dries,the fiberglass will mix with the wood. The thermal plastic is then addedas if wood was the only fiber used and extruded to the final product. Inan alternative embodiment, fiberglass is added to the process as aTwintex™ pellet that is a co-mingle of 60% fiberglass and 40%polypropylene.

In terms of strength, articles of manufacture which use fiberglass willachieve the tensile strength of some soft woods and will achieve about80% of the strength of some hard woods. With the new designs of thepresent invention and engineered nucleated polymer, a composite havingthe strength and flex modulus equal to that of wood can be created. Forexample, flex modulus of 1.2-1.3 Million, which is equal to soft wood,can be created using the composite of the invention.

As stated above, the composite material also contains thermal plastic.Thermal plastic is used to bind the fiber material together to produce asolid composite material used to form the articles of manufacture. Thethermal plastics operate by shrinking to grip the wood/fiberglass piecesas the thermal plastic cools. The preferred thermal plastics arepolyethylene and polypropylene. The most preferred thermal plastic ispolypropylene. To keep the cost of the article of manufacture made fromthe composite material low, industrial grade thermal plastic can beused. It is noted that industrial grade thermal plastics can be used,however, to get the strengths and the flex modulus shown above, anengineered grade of polymer that has been nucleated should be used. Thenucleated process adds about 20-25% to the flex modulus which iscritical in keeping the characteristics high.

Recyled (lowest grade) of polypropylene costs about 12-15 cents perpound where engineered polypropylene cost about 40-50 cents per pound.In some cases, a blend of various grades can be mixed together to reducecost without diluting the main characteristics of the product. Forexample, a blend can be used in cases where the final product does notrequire extreme strength, such as no load fence boards.

Since polyethylene is used heavily in society and can be recycled, it isreadily available and is in stable supply. Although this thermal plasticis in stable supply, it is more costly than polypropylene. In additionto being less costly, polypropylene has a number of other advantagesover polyethylene. An article of manufacture made from a compositecontaining polypropylene is stronger than one made from a compositecontaining polyethylene. Thus, polypropylene provides additionalstrength to the composite material as compared to polyethylene. Sincepolypropylene is an under utilized by-product of gasoline production,polypropylene is insulated from price fluctuations associated with themainstream plastics market. For this reason, as stated above,polypropylene is a cheaper alternative to polyethylene.

To achieve similar characteristics to wood, nucleated polymer i.e., (BPAmoco 9433) can be used. The superior strength and flex modulus makesthis a preferred choice when the composite is used in construction andheavy duty applications.

The composite material may also contain a mixture of polyethylene andpolypropylene as the thermal plastic material. Characteristics normallynot associated with each of the thermal plastics individually, may berealized when a mixture of polyethylene and polypropylene is used. Forexample, impact resistance and rigidity are two characteristics that arevery important in the production of an article of manufacture made fromthe composite material. As impact resistance increases, rigiditydecreases. In other words, the more flexible the article of manufacturemade from the composite material is, the greater the impact it canabsorb.

In order not to lose the important characteristics of the compositiondiscussed above, polyethylene can be added only in small quantitiesbefore it begins to change the overall characteristics of the composite.No more than 15% polyethylene can be added to the mixture before thecharacteristics of the composite begin to erode. Preferably, no morethan 10% polyethylene is added to mixed composite material.Polyethylene, however, can be added in a capstock mix that is layered onthe surface of the product. In this manner the body of the article ofmanufacture made form the composite is not affected.

Articles of manufacture made from composite material containing variouscombinations of polypropylene and polyethylene provide different degreesof rigidity and impact resistance. Therefore, in some cases the bestthermal plastic used to make the composite is a mixture of bothpolyethylene and polypropylene. One provider of the polypropylene usedto make the composite material is BPAMOCO. The polypropylene provided bythis company is called ACCPRO 9433 or 9434. In addition, similarproducts are also available from Solvay.

To add impact resistance to the polymer, a low density polyethylene inalmost any quantity can be added to the polypropylene without losing thetraits associated with polypropylene. If a high density polyethylene isadded to the homo-polymer to make a co-polymer, only low amounts ofpolyethylene can be added before the polypropylene traits are lost.Therefore, the percentage of polyethylene verses polypropylene dependson the density of polyethylene being added. For example, an article ofmanufacture using a composite material having 15% of polyethylene and85% of polypropylene as the thermal plastic will provide moderaterigidity and impact resistance to the article of manufacture.Alternatively, increasing the percentage of polyethylene and decreasingthe percentage of polypropylene will produce an article of manufacturewith increased rigidity and decreased impact resistance. Thus, acomposite material can be synthesized having desired characteristics notonly by varying the type of fiber material used, but also by changingthe percentage of polyethylene and polypropylene combined to make thecomposite. One skilled in the art after reading the present disclosure,would be able to prepare an article of manufacture having desiredcharacteristics by varying the percentage of polyethylene andpolypropylene used to bind the fiber material of the composite.

The composite material used to make the article of manufacture may alsoinclude enhancers which facilitate the mixing of the fiber material andthermal plastic. Examples of enhancers include, but are not limited to,fatty acids, stearic acid, benzl peroxide, dichloro-s-trianzine,isocyanates, and maleic anhydride. These enhancers are used todisaggregate the solid fibers, allowing for better adhesion between thefiber material and thermal plastic. A similar phenomena occurs when thepolypropylene is run hotter.

In one embodiment of the invention, the enhancer used is maleicanhydride. Maleic anhydride is available in two forms. The first beingas an additive that can be added to the process stream at the productionline. The second form is already pelletized in the thermal plasticmaterial and is known as Maliated Polypropylene (MAPP). MAPP isavailable from Rohm and Haas Company (Tymor 2E02 and Tymor 2500EX),Uniroyal Chemical, Eastman Chemical and Honeywell. Several other oilsare also available that serve the same purpose.

Maleic anhydride is the preferred enhancer because it has been shown toprovide a bond between fillers containing hydroxyl groups, i.e., woodfiber, and a polymer matrix, i.e., polypropylene. Therefore an articleof manufacture made from a composite material containing maleicanhydride exhibits increased strength.

The main purpose of using enhancers is to increase the percentage ofwood coverage of the fiber with the thermoplastic. This is known in theindustry as increasing the percentage of “wet out” of the wood fiber.Both the choice and the amount of enhancer used in the compositematerial is a function of the type and amount of fibers and thermalplastic material used to make the composite. The mixing compoundingconditions also play a role in choosing the amount and type of enhancer.For example, if the composite material contains wood as the fibermaterial and polypropylene as one of the thermal plastics in aco-polymer then the preferred enhancer is maleic anhydride. Since it iswithin the scope of the invention to use a combination of thermalplastics, it is also within the scope of the invention to use acombination of enhancers when making the composite material. The amountof enhancer that can be added to the fiber/plastic mixture can be up to5% by weight. Preferably up to 2% by weight and most preferably up to 1%by weight.

Once the fiber material, thermal plastic(s), and enhancer(s) are mixed,a dye coloring may be added to the composite material. The dye coloringadded to the composite material should be thoroughly mixed so that theresulting composite material is uniform in color. When the article ofmanufacture is formed from the composite material, the article ofmanufacture will also have a uniform color. The amount of the coloradded to the composite depends on the shade or intensity of colordesired. In other words, when a dark color is desired, more dye is addedto the composite material than when a lighter color scheme is desired.Either the wood mix or the plastic stream or both can be dyed to achievethe desired affect.

Articles of manufacture may be subjected to a variety of differentextremes depending on where it is ultimately used. Different additivescan be infused into the composite material used to make the article ofmanufacturer in order to reduce the damage caused by exposure to suchextremes.

For example, when the article of manufacture is made from the compositematerial that is used under conditions of extreme heat and/or flame,fire retardant additives may be added to the composite material toprevent damage to the article of manufacture. Examples of heat and/orfire retardants include Bromium or Antimoniumoxide. Similarly, if thearticle of manufacture is used in places where it may be exposed toinsects, insect resistance additives may also be added to the compositematerial to reduce or prevent damage to the article of manufacture byinsects. Insect resistance can also be achieved upon formation of thecomposite. For example, if a board is constructed from 40% wood and 60%polymer it is probable that the polymer will effectively cover the woodthus making it insect or rot resistant. In this case, no additionaladditives are needed.

To protect the article of manufacture from ultraviolet light (LV),UV-resistance additives can be added to the composite material to reduceor prevent damage to the article of manufacture by UV light. There are anumber of levels of UV protection. The first level is when UV lightprotectant chemical is added to the process stream or as an addition tothe pelletized thermal plastic. This can be either added as part of thethermal plastic pelletizing process or grouped into an additive packagethat is infused into the production stream. The main goal of the firstlevel of UV protection is to protect the thermal plastic matrix fromdegrading in the sun and causing a catostrophic failure. The UVadditives are added to the thermoplastic at less than 1% of the totalthermal plastic weight, this however will protect the plastic but willnot protect the wood chip filler. In other words, the product will stillfade to the color of aged wood since the wood chips are not protectedand will continue the fading and aging process. Similarly, a UVprotectant can also be added to the wood stream.

The second level or more advanced level of UV protection inhibits woodfading. Here a “capstock” is added to the surface of the board that hasadditives to protect against the UV wavelengths that fade wood. Thiscapstock can be applied as a co-extrusion or can be applied as a veilthat protects the surface and product against UV damage. This is acheaper method of UV protectant than level one but is more challengingto apply.

In one embodiment, a veil is specially manufactured as a polyethylene orpolypropylene veil that is less than 8 millimeters thick. This veilcontains the UV protectors added to the thermoplastic prior toapplication. Thus, the veil when applied protects the complete structureof the composite including the wood components.

To protect the article of manufacture from fungus or the like, fungusresistance additives may be added to the composite material to reduce orprevent damage to the article of manufacture by excessive growth offugii or the like. If the amount of thermal plastic or fiberglass isincreased so that is covers the wood fibers you essentially eliminatethe need to add additives designed to protect the product from rot,insects, or fungus.

To protect the article of manufacture from oxidation, heat resistanceantioxidants may be added to the composite material to reduce or preventdamages to the article of manufacture from oxidation.

The composite material may contain one or more of the additivesdescribed above depending on the conditions in which the article ofmanufacture made from the composite will be used. The composite materialmay contain up to 5% of the total weight of the composite. Preferably,the composite material may contain no more than 2% by weight of thecomposite. Most preferably, the composite material may contain no morethan 1% by weight of the composite.

After all the ingredients have been added to the composite material, thecomposite material is shaped into the article of manufacture. A film orveil or co-extrusion layer can then be added to the surface of thearticle of manufacture to provide additional durability to its surface.The film or veil is selected from the group consisting of polypropylene,polyethylene and polyester. The film or veil increases impactresistance, scuff resistance, fading and weathering.

The process of making the composite material, forming it into an articleof manufacture and adding a film and/or veil is described below.

A. Preparing the Ingredients

When wood fiber is used to make the composite material, special caremust be taken to insure that the supply of wood fiber is consistent insize, properly screened and free of contamination.

The first step in preparing the wood fiber is to sort and classify thewood source. For example, soft woods need to be sorted from hardwoodsand colored woods need to be sorted from plain woods. Pine needs to besorted from Oak and even though both Oak and Walnut are hardwoods, theyare of different color so they must also be sorted to maintainuniformity. This sorting process allows the texture and othercharacteristics of the fiber supply to be consistent, which is veryimportant in producing a consistent, quality oriented product. Sortingtexture and color before using the wood fiber to make the compositeproduces an article of manufacture with more uniform handling, andbetter structural and esthetic qualities than processes using acomposite of wood fibers straight from recycled sources. The use ofhardwood fibers as the fiber source in the composite used to make thearticle of manufacture greatly increases nail and screw holdingcapacity, as well as, increasing the overall strength of the article ofmanufacture made from the composite.

After sorting the different woods into “batches,” the product is groundinto wood chips using at least a two stage grinding process. The“batches” are first ground into a rough grind similar in appearance to agarden mulch with sizes ranging from a very small wood flour particle upthrough strips or chunks of wood that may be as large as six incheslong. The first grind is done with a large commercial sized tub orhorizontal grinder having large capacity and power. Once the first grindis completed, the product of the first grind is reground using a smallergrinder or a hammer mill which again provides a variety of sizes of woodparticles ranging from the very small wood flour category up to saw dustsize particles that may pass over a 20 mesh screen. It may take up tothree secondary grinds or more to produce a product that is acceptableand consistent in size.

As mentioned above, size and consistency of size is very important inhow well the wood fiber works in the process and directly affects thequality and attractiveness of the article of manufacture made from thecomposite material. To assure size and consistency of the wood fiber,the wood fiber is screened over a 30-50 mesh screen. Preferred fibersare those screened over a 40 mesh screen. The small and consistent sizeof wood fiber makes a very smooth product finish.

If the wood fiber source is screened too small, the weight of the boardincreases and the strength of the board decreases. This is undesirable.Wood ground and screened over a 40 mesh screen typically weights between13 and 15 pounds per cubic foot depending on whether it is soft orhardwood, soft wood being lighter. This compares to unground wood thatweighs 30-35 pounds per cubic foot. The difference in the weight iscontributed to the amount of cell or air space that is present in acubic foot of wood. Obviously, 40 mesh ground wood has far more airspace than just plain unground wood. Taking this further, the finer thegrind of the wood, the less air space and the heavier the weight of thewood fiber per cubic foot. Weight is one factor that is considered inmaking the article of manufacture. Overall, a preferred article ofmanufacture should weigh the same or less than the wood it is replacing.One way this can be achieved, as discussed above, is by using voids inthe final product. Thus, it has been found that wood ground through a 40mesh or slightly larger screen makes a product that most closelyresembles wood. Weight continues to be a problem because as you add thethermal plastic, that has a density of 40 pounds per cubic foot, theweight goes back up.

FIG. 1 shows a panel made of the composite of the invention which hasseveral strategically placed voids 10. These voids are used to reducethe overall weight and cost of the product but do to compromise theintegrity of the final product. The “void” pattern shown in FIG. 1comprises six spaces, 3 of which are mirror images of the other threeand are separated by a median line 20. The length of the panel 30 is atleast double the width of the panel 40. The voids are positioned so thatthey are off-center so as to produce a panel having more solid space onone side compared to the other.

The first void 50, is larger than the second void 60, but smaller thanthe third void 70. The three voids are positioned below one another whenmoving from the top of the panel 80 lengthwise to the bottom of thepanel 90. Three identical voids are positioned as a mirror image acrossthe median line 20. The voids provide an article of manufacture havingsuperior strength and at the same time decreased weight as compared toother wood products.

Similarly, FIG. 2 also shows a panel made of the composite of theinventor which has several strategically placed voids. Two of the voids210 are in the form of a rounded triangle and are located at each end ofa series of voids. Five of the voids 200 are “pill shaped voids that arepositioned between the two end voids 210 with a given amount of spacebetween each void. This space between and the number and size of eachvoid will vary according to the overall length of a panel. The overallstructure 250 has a solid portion 260 that surrounds each of the voids.The length of the structure 260 is at least double that of the width ofstructure 260. This arrangement of voids and solid surfaces produces astrong panel having reduced weight.

To further control the weight of the article of manufacture, a mix ofsoft woods and hardwoods may be used to produce the composite material.In this manner a lower weight is traded for the ease of processing,strength and production efficiencies of hardwoods.

Size of the wood fiber is also a factor in the strength of the articleof manufacture produced from the composite material. Strength of thearticle of manufacture is a function of fiber length and direction,which is also a function of wood fiber size. All of these factorscombined are directly related to the final weight of the article ofmanufacture made from the composite material. Wood fiber size andcomposite material produced from wood fibers sized through a 20 to 40mesh screen have the most desirable characteristic.

Moisture is another critical factor that must be controlled whenhandling wood. A moisture of 6% is desirable and allows for the mostefficient handling of the wood fiber. If moisture increases, the woodfiber tends to clump and does not handle efficiently. Drying the wood sothat it has a moisture content of less than 6% requires too much energyand the wood will regain the moisture in the storage tanks. Furtherdrying of the wood fiber will occur in the mechanical extrusion of themanufacture process.

The other ingredients added to the composite material including othersources of fiber such as fiberglass, agricultural and industrial ofproducers, enhancers and protective additives do not require any specialhandling or preparation. The fiber materials can be substituted for thewood fiber by a weight bases and the enhancers and protective additivesare used in small quantities and come ready to use straight from themanufacturers. Any grade plastics can be used to bind the wood or otherfiber materials used together and also comes “ready to use” from thesupplier.

The Process

The composite material is made using a Davis-Standard Woodtruder™extruder line. The process below is described using wood as an example.It is noted, however, that the same process can be used to produce acomposite material comprising fiberglass, industrial by-products,agricultural by-products or mixtures thereof instead of wood fiber.

The process begins by screening the wood fiber over a 20-40 mesh screento produce wood fiber having a consistent size and approximately 6%moisture. This fiber is fed into the main extruder twin screw barrel viaa gravimetric feeder. This type of feed system provides a consistentfeed of wood fiber on a weight basis. Monitoring the weight is veryimportant to get a consistent ingredient mix which affects the finalquality of the article of manufacture produced from the compositematerial.

The main barrel of the extruder is equipped with counter-rotating twinscrews that pushes the fiber material forward at a low revolutions perminute (rpm) and low shear. A heated venting area of the extruderremoves moisture from the fiber material. This allows a high volume offiber material to be dried “in-line” during production. Removal ofmoisture is critical to the process because any moisture remaining inthe wood fiber/plastic blend is converted to steam and manifests itselfin the form of foam. This can disrupt the processes and lead to anunacceptable finished article of manufacture.

In the initial extruder process, moisture is managed by a combination ofpredrying the fiber material from their ambient moisture content of 6-8%to 2-3%; and by applying a vacuum to the vent zones in the extruderbarrel during compounding to remove the remaining moisture. Temperatureduring the wood drying process is maintained at approximately 190degrees F., to avoid scorching or burning of the wood fiber. Maintainingthe temperature below the melting point of the thermal plastic avoidsdegradation of the wood fiber and a reduction in strength of the finalproduct.

In a separate extruder, the thermal plastic is melted to a temperatureof approximately at 425 degrees F. During the melting process, theadditives are added and mixed into the melted thermal plastic. By usinga separate extruder for the melting process of the thermal plastic andmixing of the additives, this process can be completed at a highertemperature separate from the wood fiber. This eliminates the risk ofscorching or burning the wood fiber during the melting and additivemixing process. The high temperature used in this process allows themelted thermal plastic to completely encapsulate the wood fiber once itsis added to the screened wood fiber. The addition of an enhancer such asmaleic anhydride, facilitates the forming of a very strong bond betweenthe wood fiber and the thermal plastic. Other enhancers discussed abovecan be added as well.

The hot thermal plastic and additive mixture is injected into the mixingsection of the main extruder barrel. Depending on the product, about 40%to about 70% of the mixture by weight is wood fiber and the thermalplastic and additives combined comprise about 30% to about 60% of themixture by weight. Additives can comprise up to about 5% of the mixtureby weight, depending on the number of additives and type of additivesselected. The mixing section thoroughly compounds theplastic/additive/fiber composite. The mix is then vacuum vented toremove any remaining moisture.

If too much wood is added, the wood fibers are not thoroughly covered bythe thermal plastic and the additive mixture. This results in a decreasein strength and physical properties of the article of manufacture madefrom the composite material. For example too much wood may cause theproduct to rot, mold and absorb water like other wood products. Anotherproblem that arises when too much wood is added to the mixture is thatthe article of manufacture made from the composite material becomesquite brittle and is subject to impact breakage. Therefore, it isessential that the amount of wood fiber added to make the composite isstrictly controlled.

The plastic/additive/fiber composite is moved through the meteringsection of the barrel to dies that provide the shape for the article ofmanufacture. It is important to shape the material while it is stillhot. The composite material can be extruded with voids in the interiorof the shape to facilitate cooling, curing and also to reduce the weightof the resulting article of manufacture. The cross-section of thearticle of manufacture has been engineered to create the voids whilemaintaining the strength of the article of manufacture. In other words,the voids are optimized to create the largest void space, lowest weightand maximum strength.

Leaving the die, the article of manufacture is cooled in two coolingtanks, each 20 feet long. In the first tank, the article of manufactureenters the tank at approximately 425 degrees F. and is cooled toapproximately 200 degrees F. using a water spray system that spraysdirectly on each surface of the article of manufacture. The water sprayis managed so that it is sprayed equally to all surfaces at the sametime so as to dissipate the heat evenly. Even dispersion of the heatprevents warping and surface irregularity of the article of manufacture.The temperature of the water used to coot the article of manufacture isheld constant at 80 degrees F. and is circulated through a system widecooling tower. To insure that the cooling water is evenly dispersed onthe article of manufacture, a matted type conveyor belt is used. Using amatted type conveyor belt permits water to be sprayed over the totalsurface of the article of manufacture resulting in even cooling. This isin contrast to a solid conveyor that would not allow the cooling waterto spray over the total surface of the article of manufacture. Inaddition, the afore-mentioned cooling tank allows the article ofmanufacture made from the extruded composite material to be cooled andpulled through the cooling tanks free of the stress normally associatedwith mechanical pullers.

In the second cooling tank, the article of manufacture is cooled fromapproximately 200 degrees F. to room temperature. In this tank, chilledwater is used to do a final cure of the article of manufacture. Thetemperature of the water used in this process is approximately 40degrees F. and is sprayed on the surfaces of the article of manufacturein the same manner as water was spayed on the surfaces of the article ofmanufacture in tank one.

After proper cooling and curing the article of manufacture is sawed todesired lengths with an in line cutoff saw. The article of manufacturecan be cut into building materials including building panels, railcarfloors, railcar walls, truck floors, truck walls, window sills, windowjams, doors, house siding, garage doors, furniture and other articles ofmanufacture that is normally made from wood or wood-like products.

Once the article of manufacture is formed a veil may be added forfurther strength and protection. A veil is a very thin film, normallyless than 8 millimeters that is added to the surface of a product forprotection against oxidation, discoloration, insect destruction, etc.For example, a veil can be added to the article of manufacture toincrease durability. The veil may be added prior to or after thematerial are cut into the desired shapes. The veil can be made frompolypropylene, polyethylene, or polyester materials. The weave of theveil is normally more important than the base material. A strong weave,such as polyester, is desirable if the material to be used as a printedor is a design surface. The weave or veil is applied to the surface ofthe product (decking board or plank) using a heating process. In otherwords, the surface of the product is heated up to approximately 400degrees F. which melts the plastic surface. In the case of polyester orweave the veil is passed into the melted plastic which extrudes throughthe weave and makes the veil part of the surface of the product. Whencooled the thermoplastic of the surface fully encompasses the veil.

In another embodiment, the veil can be co-extruded when the article ofmanufacture is being produced. This process requires a more complicateddye system but reduces the amount of time required to produce theproduct.

In the case of a polyethylene or polypropylene veil, the thermal plasticin the veil melts into the thermal plastic of the product forming onehomogenous layer that is not bonded. Thus the surface veil isincorporated into the surface of the product.

While the invention has been illustrated and described with respect tospecific illustrative embodiments and modes of practice, it will beapparent to those skilled in the art that various modifications andimprovements may be made without departing from the scope and spirit ofthe invention. Accordingly, the invention is not to be limited by theillustrative embodiment and modes of practice. For example, differentfiber material within the scope of the invention can be substituted forthe wood fiber discussed above.

1. A process for forming a composite article of manufacture comprising:(a) adding wood fibers screened through a 20-40 mesh to an extrudermixing container; (b) adding fiberglass chop about ¼ inch to about 1inch in length to the mixing container (c) heating the fibers of steps(a) and (b) in the mixing container to remove moisture; (d) contacting ahot thermal plastic additive mixture with the fibers of step (b) toproduce a fiber/thermal plastic composite; and (e) contacting thefiber/thermal plastic mixture of step (d) with a die to provide shape tothe fiber/thermal plastic composite and to produce the composite articleof manufacture, wherein the fiber/thermal plastic composite comprisesabout 35% fiberglass, about 25% wood, and about 40% plastic.
 2. Aprocess for forming a composite article of manufacture according toclaim 1 wherein the fibers are added to the mixing container by agravimetric feeder so as to provide a consistent feed of fiber to themixing container.
 3. A process for forming a composite article ofmanufacture according to claim 1 wherein the mixing container is a twinscrew extruder.
 4. A process for forming a composite article ofmanufacture according to claim 1 further comprising subjecting thefibers to a vacuum to remove additional water from the fibers.
 5. Aprocess for forming a composite article of manufacture according toclaim 1 wherein the fibers are heated to a constant temperature of about400 degrees F. to about 450 degrees F.
 6. A process for forming acomposite article of manufacture according to claim 5 wherein the fibersare heated to about 425 degrees F.
 7. A process for forming a compositearticle of manufacture according to claim 1, further comprising addingat least one additive selected from the group consisting of dyes,ultraviolet light protecting additives, flame retardants, fungusretardants additives, heat resistant antioxidants, and insect retardingadditives to the hot thermal plastic step (b) to produce a hot thermalplastic additive mixture that is contacted with the fibers of step (c).8. A process for forming a composite article of manufacture according toclaim 7 wherein the additive added to the composite article ofmanufacture is maleic anhydride.
 9. A process for forming a compositearticle of manufacture according to claim 7 wherein the compositearticle of manufacture produced is a building board or building panel.10. A process for forming a composite article of manufacture accordingto claim 8 wherein between about 0.5% to about 3% of maleic anhydride isadded to the hot thermal plastic.
 11. A process for forming a compositearticle of manufacture according to claim 1 wherein the hot thermalplastic is contacted with the fibers by injecting the hot thermalplastic into the mixing container containing the fibers.
 12. A processfor forming a composite article of manufacture according to claim 1further comprising cooling the composite article of manufacture once thecomposite article of manufacture is shaped.
 13. A process for forming acomposite article of manufacture according to claim 12 wherein thecomposite article of manufacture is first cooled to about 200 degrees F.and then subsequently cooled to room temperature.
 14. A process forforming a composite article of manufacture according to claim 13 whereinthe composite article of manufacture is cooled using a water spraysystem that sprays water on each surface of the composite article ofmanufacture.
 15. A process for forming a composite article ofmanufacture according to claim 12 further comprising cutting the cooledcomposite article of manufacture to produce composite articles ofmanufacture of desired lengths.
 16. A process for forming a compositearticle of manufacture according to claim 1 wherein the fiber is anagricultural by-product.
 17. A process for forming a composite articleof manufacture according to claim 16 wherein the agricultural by-productis selected from the group consisting of corn stalks, wheat straw, bambureeds, and sisal.
 18. A process for forming a composite article ofmanufacture according to claim 1 wherein the thermal plastic is selectedfrom the group consisting of polyethylene and polypropylene and acombination thereof.